title: The calmodulin-like protein CML43 functions as a salicylic-acid-inducible root-specific Ca(2+) sensor in Arabidopsis.
abstract: Many signalling pathways in plants are regulated by the second messenger calcium (Ca(2+)). In the standard model, Ca(2+)-sensor proteins, such as CaM (calmodulin), detect Ca(2+) signals and subsequently regulate downstream targets to advance the signal transduction cascade. In addition to CaM, plants possess many CMLs (CaM-like proteins) that are predicted to function as Ca(2+) sensors, but which remain largely uncharacterized. In the present study, we examined the biochemical properties, subcellular localization and tissue-specific distribution of Arabidopsis CML43. Our data indicate that CML43 displays characteristics typical of Ca(2+) sensors, including high-affinity Ca(2+) binding, conformational changes upon Ca(2+) binding that expose hydrophobic regions and stabilization of structure in the presence of Mg(2+) or Ca(2+). In vivo localization analysis demonstrates that CML43 resides in cytosolic and nuclear compartments. Transgenic plants expressing a CML43:GUS (β-glucoronidase) promoter reporter gene revealed that CML43 promoter activity is restricted almost exclusively to root tips under normal growth conditions. GUS reporter activity in these transgenic plants was strongly increased when exposed to the defence compound SA (salicylic acid). Furthermore, immunoblot analysis revealed that the CML43 protein accumulates following treatment with SA. Collectively, our findings suggest that CML43 functions as a Ca(2+) sensor in root tips during both normal growth and plant immune response.
authors.affiliation: *Department of Biology, Queen's University, Kingston, ON, Canada, K7L 3N6.
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Bender
authors.forename: Stephanie
authors.initials: S
authors.lastname: Dobney
authors.forename: Adenike
authors.initials: A
authors.lastname: Ogunrinde
authors.forename: David
authors.initials: D
authors.lastname: Chiasson
authors.forename: Robert T
authors.initials: RT
authors.lastname: Mullen
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Teresinski
authors.forename: Prabhjeet
authors.initials: P
authors.lastname: Singh
authors.forename: Kim
authors.initials: K
authors.lastname: Munro
authors.forename: Steven P
authors.initials: SP
authors.lastname: Smith
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Snedden
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000502:physiology; D029681:Arabidopsis Proteins / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D002147:Calmodulin / Q000235:genetics; D002478:Cells, Cultured; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D007107:Immune System / Q000378:metabolism; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D020156:Salicylic Acid / Q000494:pharmacology*; D017385:Sequence Homology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014026:Nicotiana
chemical_list: D029681:Arabidopsis Proteins; C586753:CML43 protein, Arabidopsis; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D020156:Salicylic Acid; D002118:Calcium